Viral disease strikes Ontario area fishery

[GLF]

The state Department of Environmental Conservation has announced that an outbreak of viral hemorrahagic septicemia (VHS) has been detected in southern Lake Ontario and the Thousand Islands area of the St. Lawrence River. The outbreak poses no human health threat but has caused a minor kill-off of muskellunge, an important trophy game fish in the St. Lawrence River.

VHS presents itself in a number of different ways including hemorrhaging, lesions and neurological symptoms, most of which cause extremely high mortality in any species it attacks.

While the disease is fairly common in Europe, according to DEC officials, prior to 2005 in North America it was limited to salt water species in the Atlantic and Pacific oceans. Then in 2005, a die-off of freshwater drum and round goby in the Bay of Quinte on the northern shore of Lake Ontario and muskellunge in Lake Michigan were both attributed to the disease.

According to a DEC press release dated June 13, the virus was first detected in New York last month in round gobies found dead in the St. Lawrence River. This was the first time VHS was detected in New York. Round gobies are an invasive species very likely introduced by ocean-going ships from the Black and Caspian Sea region in Europe that very likely used the St. Lawrence Seaway during the 1990s.

Round gobies continue to be found dead along the south end of Lake Ontario, eastward into the Thousand Islands area. Because this is spawning season for both the gobies and muskellunge, it is a period of high stress. This makes them vulnerable to the VHS and other disease.

If the disease attacked just gobies, the outbreak would not likely raise many eyebrows. Unfortunately, some strains of VHS can effect trout and salmon such as rainbow, brown and lake trout, and Chinook and Coho salmon. Should that strain of the disease appear on the scene, it could threaten the all-important trout and salmon population in Lake Ontario. However, to date there is no indication of an active threat to those species.

What is not yet known is how the disease entered the Great Lakes, or how long it has been there.